Alternative Ion Injector Design V.S. Morozov JLEIC Weekly R&D Meeting April 7, 2016 F. Lin

Ion Injector Scheme Baseline Consider alternative ion sources ion linac Booster L = 273 m pinj = 0.52 GeV/c Bmax = 3 T Collider ring L = 2154 m pinj = 7.95 GeV/c BB cooler DC cooler ion sources DC cooler BB cooler ion linac Booster L = 250 m pinj = 3 GeV/c Bmax = 6 T Collider ring L = 2250 m pinj = 15.9 GeV/c Bmax = 3 T Pre-booster L = 125 m pinj = 0.52 GeV/c Bmax = 1.5 T

Two Boosters Pre-booster Racetrack (no polarization issue) Accumulation and cooling L = 2/(packing factor) + insertions (injection, snake, cooling, etc.) = 2pmax/(eBmax)/0.5 + ~40 m = 125 m ~30-60 s cycle (dominated by accumulation and cooling time) Booster Simple design without accumulation and cooling Length = 2  pre-booster length = 250 m ~30-60 s cycle, 0.1-0.2 T/s

Booster Magnet Parameters JLEIC Booster

Dynamic Ranges Baseline Alternative ion sources ion linac Booster pmax / pinj = 7.95 / 0.52 = 15 Collider ring 100 / 7.95 = 13 or 200 / 7.95 = 25 BB cooler DC cooler ion sources DC cooler BB cooler ion linac Booster pmax / pinj = 15.9 / 3 = 5 Collider ring pmax / pinj = 100 / 15.9 = 6 or 200 / 15.9 = 13 Pre-booster pmax / pinj = 3 / 0.52 = 6

Space Charge Assuming sc ~ L / (2) and normalizing to the baseline booster Baseline Alternative ion sources ion linac Booster SC factor = 1 Collider ring SC factor = 0.07 BB cooler DC cooler ion sources ion linac Booster SC factor = 0.05 Collider ring SC factor = 0.02 BB cooler DC cooler Pre-booster SC factor = 0.46

Transition Energies Baseline Alternative ion sources DC cooler BB cooler ion linac Booster Imaginary tr Collider ring pinj = 7.95 GeV/c tr = 12.46 Etr crossed by all ions ion sources DC cooler BB cooler ion linac Booster Imaginary tr Collider ring pinj = 15.9 GeV/c tr = 12.46 No Etr crossing for p Pre-booster Below transition

Stored Magnetic Field Energy Assumptions Normalized to the baseline ion collider ring (BCR), UBCR = 1 Scaling U ~ Bmax2 V ~ Bmax2 max2 L ~ Bmax2 L / pmin Aperture may not quite scale with the beam size because of Sagitta Closed orbit allowance Cooling Different focusing (average  functions) in different rings Different beam stay-clear requirements in different rings But, besides lower magnet cost, smaller aperture and beam size mean Cheaper power supplies Possibly less stringent multipole requirements Simpler dynamics, beta-squeeze, collimation, etc.

Stored Magnetic Field Energy Baseline Alternative ion sources DC cooler BB cooler ion linac Booster U = 1.9 Collider ring U = 1 ion sources DC cooler BB cooler ion linac Booster U = 1.2 Collider ring U = 0.5 Pre-booster U = 0.2

Conclusions Advantages of the alternative scheme Better overall performance in terms of required dynamic ranges, space charge, and transition energy crossing Simpler individual ring designs Simpler operation, no need for complicated cycle in the baseline booster Simpler magnet requirements Judging by the stored magnetic field energy, not necessarily more expensive Better pathway to 200 GeV Disadvantages ~150 m longer (mostly warm) beam line and tunnel length Higher field (but smaller aperture) magnets in the booster Possibly somewhat longer total cycle but can still be 10 min (with 30 s cycles in the pre-booster and booster) or 20 min (with 1 min cycles)

Backup

Ion Collider Ring Figure-8 ring with a circumference of 2153.9 m Two 261.7 arcs connected by two straights crossing at 81.7 Vertical doglegs to be added R = 155.5 m Arc, 261.7 IP disp. supp./ geom. match #3 geom. match #1 geom. match #2 det. elem. disp. supp. norm.+ SRF tune tromb.+ match beam exp./ elec. cool. ions 81.7 future 2nd IP Polarimeter

Ion Collider Ring Parameters All design goals achieved Resulting collider ring parameters Proton energy range GeV 20(8)-100 Polarization % > 70 Detector space m -4.6 / +7 Luminosity cm-2s-1 > 1033 Circumference m 2153.89 Straights’ crossing angle deg 81.7 Horizontal / vertical beta functions at IP *x,y cm 10 / 2 Maximum horizontal / vertical beta functions x,y max ~2500 Maximum horizontal dispersion Dx 3.28 Horizontal / vertical betatron tunes x,y 24(.38) / 24(.28) Horizontal / vertical natural chromaticitiesx,y -101 / -112 Momentum compaction factor  6.45  10-3 Transition energy tr 12.46 Normalized horizontal / vertical emittance x,y µm rad 0.35 / 0.07 Horizontal / vertical rms beam size at IP *x,y µm ~20 / ~4 Maximum horizontal / vertical rms beam size x,y mm 2.8 / 1.3

Arc FODO Cell Basic building block of the arcs Dipoles Quadrupoles Length of 22.8 m = 1.5  electron FODO cell lengths (26 cells per arc) Betatron phase advance of 90 in each plane Dipoles Magnetic/physical length of 8/8.28 m (implemented as two 4 m long pieces) Bending angle of 73.3 mrad (4.2), bending radius of 109.1 m, sagitta of 18.3 mm Field of 3.06 T at 100 GeV/c x aperture = (4 cm+sagitta/2) = 5 cm, y aperture = 3 cm (10 + 1 cm orbit allowance) Quadrupoles Magnetic/physical length of 0.8/0.9 m Field gradients of 52.7/-52.9 T/m at 100 GeV/c Field of 2.1/-2.1 T at 40 mm radius Sextupole/corrector package next to each quadrupole Magnetic/physical length of 0.5/0.6 m 3 T at 40 mm focusing sextupole adds 34.8/-7.1 units of x/y chromaticity 3 T at 40 mm defocusing sextupole adds -3.7/18.1 units of x/y chromaticity BPM next to each quadrupole Physical length of 0.15 m

Complete Ion Collider Ring Lattice Optics of a complete ring with all sections incorporated and matched Arc 1 Straight 1 Arc 2 Straight 2 Arc 1 ions IP

Element Count Dipoles: 133 Regular: 127 super-ferric, B < 3.06 T Special: 2 for IR (discussed later) + 4 cos() super-conducting, B < 4.7 T Quadrupoles: 205 Regular: 155 with integrated field < 48 T (60 T/m) Regular*: 44 with integrated field < 72 T (90 T/m, these may require separate design, e.g. increased length) Special: 6 final-focusing quadrupoles (discussed later) Sextupoles: 125 Maximum pole-tip field ~1.5 T

Misalignment & Multipole Sensitivity Misalignment and DA after orbit, beta beat, tune, chromaticity & coupling correction Sensitivity to multipoles in super-ferric arc dipoles ( < 200 m) per TAMU specs. Specs for large- magnets are under investigation   Dipole Quadrupole [FFQ] Sextupole BPM noise Corrector x (mm) 0.3 0.3 [0.03] 0.02 - y (mm) rms roll (mrad) 0.3 [0.05] s (mm) Strength error (%) 0.1 0.2 [0.03] 0.2 0.01 Δp/p = 0 different seeds at IP ~(50) in x & y D Q S ALL 133 205 75 IR area, β > 1 km 2 6 β > 200 m 21 19 8 only  < 200 m ~ (50) in x & y Multipole errors of super-ferric dipole at radius 20 mm (unit: 10^-4) multipole type systematic -0.151 -0.537 0.126 0.850 0.714 0.366 -0.464 -0.410 0.009 0.027 Random  

Aperture Specifications Regular dipoles Closed orbit allowance, COA = 1 cm Sagitta of 4 m section, SG  1 cm Horizontal rms beam size at injection, x inj = (xx inj + (Dxp/pinj)2)1/2  3 mm Vertical rms beam size at injection, y inj = (yy inj)1/2  2 mm Horizontal aperture, HA = 10 x inj + SG + COA = 5 cm Vertical aperture, VA = 10 y inj + COA = 3 cm Regular quadrupoles HA = VA = 10 x inj + COA = 4 cm

Preliminary Injection Optics Cannot inject with collision optics because the beam would be too large in the interaction region  Need beta squeeze Multipole sensitivity in this mode needs to be studied IP

(dipole x aperture – sagitta), quad aperture Beam Size at Injection Assuming pinj = 8 GeV/c, x inj norm = y inj norm = 1 m, p/pinj = 110-3 The peaks in the beam size can be brought down to within the aperture quad y aperture dipole y aperture (dipole x aperture – sagitta), quad aperture